How to stop 2002 Mercruiser 5.0 MPI fuel pump whine?

[mohlmann]

Hi Folks,
I've got a 2002 Mercruiser 5.0 MPI with a bravo 3 outdrive, I've replace the lift fuel pump and the high pressure fuel pump, the fuel pressure regulator. The fuel pressure is at spec. the engine starts and runs perfectly.
the problem is that at idle there is a high pitched and very annoying whine coming from the high pressure pump. I replaced the high pressure pump once and it made a whine, so bought another one and it also made this whine.

Any suggestion on how to get rid of the whine?

thanks,
rick

 

[wellcraft-classic210]

while i am not highly familiar with your noise and pump ---

--wondering if if its related to external or internal vibration --

if its external ( as in shaking around )
could it be mounted with rubber washers / rubber padded straps etc ??

if its internal

wondering if insulation can be used to muffle the noise

 

[Scott Danforth]

not sure you have a problem

HP fuel pumps whine

its the nature of the beast

you may be able to wrap some sound insulation around the pump module.

 

[alldodge]

Do you have the inline filter along with the canister filter?
What's your serial number?

 

[metsfan3197843]

The IAC makes an obnoxious whine at idle if the little muffler filter is missing. I couldn’t believe how much of a difference that little piece of foam made on my 5.0 MPI. Chance it could be that noise you are hearing and not a fuel pump?

 

[mohlmann]

AllDodge: i do have an inline filter in addition to canister filter, the s/n is :0m603355
wellcraft-classic210: it has rubber pads and i added additional rubber
metsfan3197843: i know exactly what you're referring to and I bought the little muffler and it cut out that noise, but i unplugged the high pressure pump and it ran on the low pressure/lift pump and the noise was gone. I also unplugged the lift pump and it ran and oddly the noise was lessened but still there from high pressure pump

Scott Danforth: the boat is a steigercraft block island and it has a big fiber glass cover, i was thinking of sound proofing that if i couldnt figure out a way to eliminae the whine...

thanks guys for your responses, much appreciated,


rick

 

[alldodge]

The low pressure (boost) pump was added to help stop vapor lock. The inline prefilter was added to protect the LP pump. The pressure is boosted to the HP pump and does cause the pump to make more noise. The motor will run fine with just the HP one, but as you say it still makes noise.

I'm amazed the motor ran with just the low pressure pump. The Gen 3 cool fuel modules put both pumps in the same container to reduce the noise, but also increased the replacement filter parts quite a bit.

Was the original pump and regulator replaced for the noise issue only or was there another reason? Just wondering if this is an aftermarket pump issue, if not then I guess there is no fix other then to go to a different type

 

[muc]

You have an open recall on this engine. contact a MerCruiser dealer and get it fixed before it burns down. Mention Service Bulletin 2006-02
For the fuel pump whine, I suggest you vacuum test the fuel system. Its highly likely That after replacing 2 pumps and having the same problem ---- the pump isn't the problem.
If there is too much restriction in the fuel withdrawal tube, anti-siphon valve, inline filter or fuel line from tank to filter a pump will whine.

 

[QBhoy]

Sure it’s not the iac ? Other than that, my fuel pump makes a whistl type noise coming up the revs. I think where the hp is coming online.

 

[mohlmann]

AllDodge: Was the original pump and regulator replaced for the noise issue only or was there another reason?
when i first bought the boat about 3 years ago, it ran but would take forever to start, i.e. lots of cranking, both when it cold and even after all warmed up. so after reading on forums etc, i did a fuel pressure test and the rail and it was way out of spec. Additionally i used a vacuum pump to check the fp regulator and it could not hold a vacuum. So i ordered new fp regulator, new hp fuel pump and while i was poking around, i discovered that the boost pump wasnt ever working. so i replaced all 3...

MUC: i am going to do a test with my vacuum pump tool to see if it is really hard to pull the fuel through all those components. I was also thinking of running a rubber fuel line to a 2 gallon gas tank to eliminate several components and see if the noise goes away.

QBHoy, i un plugged high pressure and it ran on lift pump and noise completely went away.. I also replaced the little filter that reduces noise in the iac intake

Here is one more piece of info: this is a GM engine that has been marinized by Mercury. there is still the automobile fp regulator left on. I read online when i was trying to figure out the hard start that the fp regulator that does the regulating is on the cool fuel module and that the left over fuel pressure regulator set up didn't do anything, so i disconnected the vacuum line going to the automobile fuel pressure regulator.

I guess i could re connect and see if it makes any diff.

thanks for the replies guys, much appreciated.

I'll update this thread if I find a solution.

Rick

 

[alldodge]

The fuel pressure is at spec

Stated this in first post, but to make sure the fuel pressure (FP) should be 43 psi at 1800 rpm.

Don't worry if the FP regulator is an automotive one or not (so far as part number), there is no difference. Mke sure you have the correct FP reading at the rail.

The vacuum reading reading should be taken with the motor running and a vacuum gauge placed in line between tank and fuel filter. When running it should not be more then 2 inHg